Relay pagination algorithm
This commit is contained in:
Blaine Bublitz
parent
43cf45317d
commit
e696061666
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@ -10,29 +10,98 @@ pub use connection_type::Connection;
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pub use cursor::Cursor;
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/// Connection query operation
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pub enum QueryOperation<'a> {
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/// Forward query
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Forward {
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pub enum QueryOperation {
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/// Return all results
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None,
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/// Return all results after the cursor
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After {
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/// After this cursor
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after: Option<&'a str>,
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/// How many records did this query return
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limit: usize,
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after: Cursor,
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},
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/// Backward query
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Backward {
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/// Return all results before the cursor
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Before {
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/// Before this cursor
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before: Option<&'a str>,
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/// How many records did this query return
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before: Cursor,
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},
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/// Return all results between the cursors
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Between {
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/// After this cursor
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after: Cursor,
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/// But before this cursor
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before: Cursor,
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},
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/// Return the amount of results specified by `limit`, starting from the beginning
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First {
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/// The maximum amount of results to return
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limit: usize,
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},
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/// Return the amount of results specified by `limit`, starting after the cursor
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FirstAfter {
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/// The maximum amount of results to return
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limit: usize,
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/// After this cursor
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after: Cursor,
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},
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/// Return the amount of results specified by `limit`, starting from the beginning but ending before the cursor
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FirstBefore {
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/// The maximum amount of results to return
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limit: usize,
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/// Before this cursor
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before: Cursor,
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},
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/// Return the amount of results specified by `limit`, but between the cursors. Limit includes beginning results.
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FirstBetween {
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/// The maximum amount of results to return
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limit: usize,
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/// After this cursor
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after: Cursor,
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/// But before this cursor
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before: Cursor,
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},
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/// Return the amount of results specified by `limit`, but before the end
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Last {
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/// The maximum amount of results to return
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limit: usize,
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},
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/// Return the amount of results specified by `limit`, but before the end. Must not include anything before the cursor.
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LastAfter {
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/// The maximum amount of results to return
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limit: usize,
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/// After this cursor
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after: Cursor,
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},
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/// Return the amount of results specified by `limit`, but before the cursor
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LastBefore {
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/// The maximum amount of results to return
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limit: usize,
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/// Before this cursor
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before: Cursor,
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},
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/// Return the amount of results specified by `limit`, but between the cursors. Limit includes ending results.
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LastBetween {
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/// The maximum amount of results to return
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limit: usize,
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/// After this cursor
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after: Cursor,
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/// But before this cursor
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before: Cursor,
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},
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/// An invalid query was made. For example: sending `first` and `last` in the same query
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Invalid,
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}
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/// Empty edge extension object
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#[async_graphql_derive::SimpleObject(internal)]
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pub struct EmptyEdgeFields;
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// Temporary struct for to store values for pattern matching
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struct Pagination {
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after: Option<Cursor>,
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before: Option<Cursor>,
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first: Option<i32>,
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last: Option<i32>,
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}
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/// Data source of GraphQL Cursor Connections type
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///
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/// `Edge` is an extension object type that extends the edge fields, If you don't need it, you can use `EmptyEdgeFields`.
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@ -60,23 +129,37 @@ pub struct EmptyEdgeFields;
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/// type Element = i32;
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/// type EdgeFieldsObj = DiffFields;
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///
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/// async fn query_operation(&self, operation: &QueryOperation<'_>) -> FieldResult<Connection<Self::Element, Self::EdgeFieldsObj>> {
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/// async fn query_operation(&self, operation: &QueryOperation) -> FieldResult<Connection<Self::Element, Self::EdgeFieldsObj>> {
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/// let (start, end) = match operation {
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/// QueryOperation::Forward {after, limit} => {
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/// let start = after.and_then(|after| base64::decode(after).ok())
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/// QueryOperation::First {limit} => {
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/// let start = 0;
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/// let end = start + *limit as i32;
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/// (start, end)
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/// }
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/// QueryOperation::Last {limit} => {
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/// let end = 0;
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/// let start = end - *limit as i32;
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/// (start, end)
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/// }
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/// QueryOperation::FirstAfter {after, limit} => {
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/// let start = base64::decode(after.to_string())
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/// .ok()
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/// .and_then(|data| data.as_slice().read_i32::<BE>().ok())
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/// .map(|idx| idx + 1)
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/// .unwrap_or(0);
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/// let end = start + *limit as i32;
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/// (start, end)
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/// }
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/// QueryOperation::Backward {before, limit} => {
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/// let end = before.and_then(|before| base64::decode(before).ok())
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/// QueryOperation::LastBefore {before, limit} => {
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/// let end = base64::decode(before.to_string())
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/// .ok()
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/// .and_then(|data| data.as_slice().read_i32::<BE>().ok())
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/// .unwrap_or(0);
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/// let start = end - *limit as i32;
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/// (start, end)
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/// }
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/// // You should handle all cases instead of using a default like this
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/// _ => (0, 10)
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/// };
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///
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/// let nodes = (start..end).into_iter().map(|n| (base64::encode(n.to_be_bytes()).into(), DiffFields {diff: n - 1000}, n)).collect();
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@ -87,8 +170,8 @@ pub struct EmptyEdgeFields;
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/// #[Object]
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/// impl QueryRoot {
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/// async fn numbers(&self, ctx: &Context<'_>,
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/// after: Option<String>,
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/// before: Option<String>,
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/// after: Option<Cursor>,
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/// before: Option<Cursor>,
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/// first: Option<i32>,
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/// last: Option<i32>
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/// ) -> FieldResult<Connection<i32, DiffFields>> {
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@ -133,42 +216,122 @@ pub trait DataSource: Sync + Send {
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async fn query(
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&self,
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_ctx: &Context<'_>,
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after: Option<String>,
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before: Option<String>,
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after: Option<Cursor>,
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before: Option<Cursor>,
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first: Option<i32>,
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last: Option<i32>,
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) -> FieldResult<Connection<Self::Element, Self::EdgeFieldsObj>> {
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let operation = if let Some(after) = &after {
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QueryOperation::Forward {
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after: Some(after),
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limit: match first {
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Some(value) => value.max(0) as usize,
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None => 10,
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},
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}
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} else if let Some(before) = &before {
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QueryOperation::Backward {
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before: Some(before),
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limit: match last {
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Some(value) => value.max(0) as usize,
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None => 10,
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},
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}
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} else if let Some(first) = first {
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QueryOperation::Forward {
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after: None,
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limit: first.max(0) as usize,
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}
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} else if let Some(last) = last {
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QueryOperation::Backward {
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let pagination = Pagination {
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first,
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last,
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before,
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after,
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};
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let operation = match pagination {
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// This is technically allowed according to the Relay Spec, but highly discouraged
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Pagination {
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first: Some(_),
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last: Some(_),
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before: _,
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after: _,
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} => QueryOperation::Invalid,
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Pagination {
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first: None,
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last: None,
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before: None,
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limit: last.max(0) as usize,
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}
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} else {
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QueryOperation::Forward {
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after: None,
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limit: 10,
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}
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} => QueryOperation::None,
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Pagination {
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first: None,
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last: None,
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before: Some(before),
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after: None,
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} => QueryOperation::Before { before },
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Pagination {
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first: None,
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last: None,
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before: None,
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after: Some(after),
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} => QueryOperation::After { after },
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Pagination {
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first: None,
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last: None,
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before: Some(before),
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after: Some(after),
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} => QueryOperation::Between { after, before },
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Pagination {
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first: Some(limit),
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last: None,
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before: None,
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after: None,
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} => QueryOperation::First {
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limit: limit.max(0) as usize,
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},
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Pagination {
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first: Some(limit),
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last: None,
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before: Some(before),
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after: None,
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} => QueryOperation::FirstBefore {
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limit: limit.max(0) as usize,
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before,
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},
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Pagination {
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first: Some(limit),
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last: None,
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before: None,
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after: Some(after),
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} => QueryOperation::FirstAfter {
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limit: limit.max(0) as usize,
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after,
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},
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Pagination {
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first: Some(limit),
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last: None,
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before: Some(before),
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after: Some(after),
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} => QueryOperation::FirstBetween {
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limit: limit.max(0) as usize,
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after,
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before,
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},
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Pagination {
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first: None,
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last: Some(limit),
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before: None,
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after: None,
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} => QueryOperation::Last {
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limit: limit.max(0) as usize,
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},
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Pagination {
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first: None,
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last: Some(limit),
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before: Some(before),
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after: None,
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} => QueryOperation::LastBefore {
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limit: limit.max(0) as usize,
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before,
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},
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Pagination {
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first: None,
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last: Some(limit),
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before: None,
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after: Some(after),
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} => QueryOperation::LastAfter {
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limit: limit.max(0) as usize,
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after,
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},
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Pagination {
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first: None,
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last: Some(limit),
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before: Some(before),
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after: Some(after),
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} => QueryOperation::LastBetween {
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limit: limit.max(0) as usize,
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after,
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before,
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},
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};
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self.query_operation(&operation).await
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@ -177,6 +340,6 @@ pub trait DataSource: Sync + Send {
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/// Parses the parameters and executes the query，Usually you just need to implement this method.
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async fn query_operation(
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&self,
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operation: &QueryOperation<'_>,
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operation: &QueryOperation,
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) -> FieldResult<Connection<Self::Element, Self::EdgeFieldsObj>>;
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}
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@ -9,36 +9,145 @@ impl<'a, T: Sync> DataSource for &'a [T] {
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async fn query_operation(
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&self,
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operation: &QueryOperation<'_>,
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operation: &QueryOperation,
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) -> FieldResult<Connection<Self::Element, Self::EdgeFieldsObj>> {
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let (start, end) = match operation {
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QueryOperation::Forward { after, limit } => {
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let start = after
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.and_then(|after| base64::decode(after).ok())
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QueryOperation::None => {
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let start = 0;
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let end = self.len();
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(start, end)
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}
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QueryOperation::After { after } => {
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let start = base64::decode(after.to_string())
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.ok()
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.and_then(|data| data.as_slice().read_u32::<BE>().ok())
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.map(|idx| (idx + 1) as usize)
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.unwrap_or(0);
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let end = self.len();
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(start, end)
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}
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QueryOperation::Before { before } => {
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let end = base64::decode(before.to_string())
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.ok()
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.and_then(|data| data.as_slice().read_u32::<BE>().ok())
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.map(|idx| idx as usize)
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.unwrap_or_else(|| self.len());
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let start = 0;
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(start, end)
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}
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QueryOperation::Between { after, before } => {
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let start = base64::decode(after.to_string())
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.ok()
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.and_then(|data| data.as_slice().read_u32::<BE>().ok())
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.map(|idx| (idx + 1) as usize)
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.unwrap_or(0);
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let end = base64::decode(before.to_string())
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.ok()
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.and_then(|data| data.as_slice().read_u32::<BE>().ok())
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.map(|idx| idx as usize)
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.unwrap_or_else(|| self.len());
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(start, end)
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}
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QueryOperation::First { limit } => {
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let start = 0;
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let end = (start + *limit).min(self.len());
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(start, end)
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}
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QueryOperation::FirstAfter { after, limit } => {
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let start = base64::decode(after.to_string())
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.ok()
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.and_then(|data| data.as_slice().read_u32::<BE>().ok())
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.map(|idx| (idx + 1) as usize)
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.unwrap_or(0);
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let end = (start + *limit).min(self.len());
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(start, end)
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}
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QueryOperation::Backward { before, limit } => {
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let end = before
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.and_then(|before| base64::decode(before).ok())
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QueryOperation::FirstBefore { before, limit } => {
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let end_cursor = base64::decode(before.to_string())
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.ok()
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.and_then(|data| data.as_slice().read_u32::<BE>().ok())
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.map(|idx| idx as usize)
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.unwrap_or_else(|| self.len());
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let start = if end < *limit { 0 } else { end - *limit };
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let start = (end_cursor - *limit).max(0);
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let end = (start + *limit).min(end_cursor);
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(start, end)
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}
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QueryOperation::FirstBetween {
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after,
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before,
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limit,
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} => {
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let start = base64::decode(after.to_string())
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.ok()
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.and_then(|data| data.as_slice().read_u32::<BE>().ok())
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.map(|idx| (idx + 1) as usize)
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.unwrap_or(0);
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let end_cursor = base64::decode(before.to_string())
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.ok()
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.and_then(|data| data.as_slice().read_u32::<BE>().ok())
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.map(|idx| idx as usize)
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.unwrap_or_else(|| self.len());
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let end = (start + *limit).min(end_cursor);
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(start, end)
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}
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QueryOperation::Last { limit } => {
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let end = self.len();
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let start = (end - *limit).max(0);
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(start, end)
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}
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QueryOperation::LastAfter { after, limit } => {
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let end = self.len();
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let start_cursor = base64::decode(after.to_string())
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.ok()
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.and_then(|data| data.as_slice().read_u32::<BE>().ok())
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.map(|idx| (idx + 1) as usize)
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.unwrap_or(0);
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let start = (end - *limit).max(start_cursor);
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(start, end)
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}
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QueryOperation::LastBefore { before, limit } => {
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let end = base64::decode(before.to_string())
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.ok()
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.and_then(|data| data.as_slice().read_u32::<BE>().ok())
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.map(|idx| idx as usize)
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.unwrap_or_else(|| self.len());
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let start = (end - *limit).max(0);
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(start, end)
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}
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QueryOperation::LastBetween {
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after,
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before,
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limit,
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} => {
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let start_cursor = base64::decode(after.to_string())
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.ok()
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.and_then(|data| data.as_slice().read_u32::<BE>().ok())
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.map(|idx| (idx + 1) as usize)
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.unwrap_or(0);
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let end = base64::decode(before.to_string())
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.ok()
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.and_then(|data| data.as_slice().read_u32::<BE>().ok())
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.map(|idx| idx as usize)
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.unwrap_or_else(|| self.len());
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let start = (end - *limit).max(start_cursor);
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(start, end)
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}
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QueryOperation::Invalid => {
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let start = 0;
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let end = 0;
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(start, end)
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}
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};
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let mut nodes = Vec::with_capacity(end - start);
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for (idx, item) in self[start..end].iter().enumerate() {
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nodes.push((
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base64::encode((idx as u32).to_be_bytes()).into(),
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EmptyEdgeFields,
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item,
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));
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if nodes.capacity() != 0 {
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for (idx, item) in self[start..end].iter().enumerate() {
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nodes.push((
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base64::encode((idx as u32).to_be_bytes()).into(),
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EmptyEdgeFields,
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item,
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));
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}
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}
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Ok(Connection::new(None, start > 0, end < self.len(), nodes))
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